Technical Field
The present invention relates to a rotor securing arrangement and a rotating electric machine having the rotor securing arrangement.
Related Art
A double-stator motor, as disclosed Japanese Patent Application Laid-Open Publication No. 2013-090531, can use a magnet prone to demagnetization, such as ferrite, and is intended to facilitate manufacturing. This double-stator motor includes an annular rotor connected to a rotary shaft to rotate in unison with the rotary shaft, an inner stator arranged radially inside the rotor, and an outer stator arranged radially outside the rotor.
With the double-stator motor as disclosed Japanese Patent Application Laid-Open Publication No. 2013-090531, maximizing the motor output within a limited housing space requires axial ends of the rotor core and the stator core coupled in magnetic circuit with each other to be aligned, or the axial end of the rotor core to be extended toward U-shape bridges. However, whether the rotor core is directly or indirectly connected to the rotary shaft using coupling members, such as rivets or the like, only head portions of the connecting members will protrude from the axial end face of the rotor, which requires part or the whole of a plate holding the outer and inner stator cores or U-shape bridges to be extended in the axial direction to avoid the protruding head portions. This leads to increase of the axial length of the motor.
The disc for connecting the rotor to the rotary shaft is commonly made of the same steel material as the shaft to eliminate looseness between the shaft and the disc coupled to the shaft caused by linear expansion. However, since the rotor core is coupled to the disc, magnetic leakage will occur from the magnet through the disc, which may lead to performance degradation.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing a rotor securing arrangement and a rotating electric machine having the same, capable of reducing the axial length of the rotating electric machine and further capable of preventing magnetic leakage from a magnet of a rotor through a disc and thereby preventing performance degradation.